Program Summary The long term goal of the program in Embryology: Methods and Concepts in Modern Developmental Biology at the Marine Biological Laboratory (MBL) is to polish pre- and postdoctoral trainees into the leaders of research in developmental, regenerative, and stem cell biology. To accomplish this goal, the course comprehensively covers the paradigms, problems, and technologies of developmental biology cast within the comparative framework of animal evolution. The program is offered within the unique physical and intellectual environment of the summer at MBL, where hundreds of scientists and trainees come together to train in a variety of biomedically relevant fields, thereby providing ample opportunities for cross-disciplinary collaborations and discussions. Twenty-four students are selected each year from a very talented pool of diverse national and international applicants. The course curriculum involves a series of formal lectures, informal seminars, extended discussions, and an immersive laboratory focused on discovery research delivered over a six-week period in the summer. The teaching faculty are high-profile scientists in the field from across the US and around the world. Six modules, each one week long, are staffed by two full-time Course Directors, three to four faculty instructors, outside lecturers, and course and teaching assistants. The themes of the modules change from year-to-year as important advances in the field occur. Students are exposed to a wide variety of embryonic systems including well-established models, both genetic (fruit flies, nematodes, zebrafish, mouse) and experimental (chickens, sea urchins, frogs, ascidians). Students also encounter a range of non-traditional models such as marine organisms that exemplify animal diversity (e.g., cnidarians, nemerteans, planarians, crustaceans, molluscs, annelids, hemichordates, ctenophores). This broad coverage allows for a close examination of novel developmental strategies and mechanisms that may provide new insights into human related embryonic processes. Hands-on methodologies used to explore development involve surgical manipulation (cell ablation, tissue grafting) as well as molecular genetic tools (CRISPR/cas9, RNAi, electroporation) and cell biological approaches (use of genetic reporters to analyze cell lineage and migratory behavior). Students apply cutting-edge microscopy and imaging technologies (e.g., confocal imaging, light sheet microscopy, super-resolution microscopy and 3D time lapse) using state-of-the-art instrumentation, reagents, and methods. Conceptual topics include cell specification and differentiation, pattern formation, embryonic axis formation, morphogenesis, intercellular signaling, transcriptional regulation, organogenesis, regeneration, and comparative embryology. Students are challenged to formulate and test hypotheses, and work tirelessly in the well-equipped research and learning environment at the MBL. Alumni regularly state that this course was one of the most transformative and influential training experiences in their lives.